| Summary: | 博士 === 國立交通大學 === 機械工程系所 === 95 === Polymer blends can modify physical characteristics of raw materials, creating a novel performance. In this study, polycarbonate (PC) and crystalline polymer, isotatic polypropylene (iPP) or Poly ether ether ketone (PEEK), are extruded by a mechanical blending extruder to process novel materials with various characteristics in raw materials. A reciprocated mechanism for shearing is also designed to perform long-term shearing at a high shear rate in the packing stage of injection molding and to investigate how processing history affects product performance. The first part of this study focuses mainly on the phase morphologies and mechanical properties affected by the various processing histories. Additionally, experiments involving specimen preparation approaches are performed, along with observations made to examine and discuss the change of phase morphology with the measured results of mechanical property for the molding specimens. Experimental results indicate that adding a slight amount of PC into the iPP matrix, i.e., less than 20%, increases the tensile strength of specimens. Additionally, the phase orientation is improved and most of the tensile strength of the blends increases after shearing. The tensile strength of the shearing specimens with a PC content under 25% exceeds that of the normal specimens of pure iPP. Moreover, a higher iPP content corresponds to a higher tensile strength after shearing. The feasibility of using PC/iPP blends in industrial applications is also investigated, indicating that shearing is valuable in industrial applications when the PC content in PC/iPP blends is under 25%.
Whereas heat resistance, thermal stability and the effect of interaction on PC/PEEK blends have received limited attention in literature, the second part of this study attempts not only to determine whether PC should be blended with PEEK, but also to elucidate the phase morphology of the PC/PEEK blends by optical microscopy (OM), following specific etching procedures. According to those results, acetone and DETA can be used to prepare specimens if PC is the minor phase in PC/PEEK blends. Furthermore, 50% CrO3 should be used to prepare specimens if PEEK is the minor phase. PC and PEEK are quite miscible with each other in a 20/80 ratio, explaining why etching methods are ineffective in discriminating between PEEK and PC phases. DSC measurements reveal that the PC/PEEK blends, except for PC/PEEK(20/80), may be partially miscible, as evidenced by the decrease in the differences between the Tg values of PC and PEEK with increasing PEEK content. However, specific compositions, e.g., the PC/PEEK (20/80) blend, are miscible in the melting state and exhibit a single Tg. This finding was also confirmed by the enthalpy relaxation method, phase morphologies and the net PC weight loss determined by holding-temperature degradation.
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